Vital organ failure is one of the most critical problems facing the health care field today. In the United States, the number of patients awaiting an organ for transplant has risen above 75,000. Despite advances in living donor organ transplantation, a severe shortage of donor organs available to these patients remains as the crux of the problem. Mechanical devices are one approach to addressing the organ shortage. Xenografts are another approach. However, due the intrinsic limitations of these technologies, these approaches are only partial solutions to the problem.
Tissue engineering can be a complete and permanent solution to the problem of organ loss or failure, but the primary challenge for tissue engineering vital organs is the requirement for a vascular supply for nutrient and metabolite transfer. To date, tissue engineering has relied on the in-growth of blood vessels into tissue-engineered devices to achieve permanent vascularization. This strategy has worked well for many tissues. However, it falls short for thick, complex tissues such as large vital organs, including liver, kidney, and heart.
In parallel to recent tissue engineering advances, the rapidly emerging field of MicroElectroMechanical Systems (MEMS) has penetrated a wide array of applications, in areas as diverse as automotives, inertial guidance and navigation, microoptics, chemical and biological sensing, and biomedical engineering. Control of features down to the submicron level can routinely be achieved in mechanical structures.
Several groups have used these highly precise silicon arrays to control cell behavior and study gene expression and cell surface interactions (See, published PCT patent application WO 00/66036; Kaihara et al., Tissue Eng 6(2): 105-17 (April 2000), each incorporated herein by reference). However, classical MEMS techniques are planar in nature. Silicon micromachining technology is often referred to as the “planar technology” (Grove A S, Physics and Technology of Semiconductor Devices, Wiley, New York, 1967). MEMS technology has not previously been adapted to the generation of thick, three-dimensional vascularized tissues.
Accordingly, there is a need in the art for precise fabrication methods capable of forming thick, three-dimensional tissues having an intrinsic blood supply system.